Pipeline flow tee

ABSTRACT

A method and apparatus for passing a pipeline sphere through a flow tee disposed in a pipeline whereby fluid flowing through the pipeline may selectively be flowed through at least one of the outlets of the run of the flow tee or the branch outlet of the flow tee while preventing the sphere from entering the branch outlet. A gap is formed in the run of the flow tee at its junction with the branch outlet so that fluid may pass through either the run or the branch outlet when the run is occupied by a pipeline sphere. This gap is approximately equal to between 1 1/2 and 2 times the diameter of the sphere.

United States Patent Bell et al. I 1 July 18, 1972 54] PIPELINE FLOW TEEr 3,166,094 1/1965 Eagleton ....137/544 172 Inventors: Howard F. Bell;John A. Scheineman, both 221 3/1322 ta g: 33?}; 3,51 1,272 5/1970Lathrop 137/544 [73] Assignee: Shell Oil Company, New York, NY.

- FOREIGN PATENTS OR APPLICATIONS 22 Filed: Feb. 11, 1970 I I 964,683 7/l 964 Great Brltam ..285/ l 56 [211 Appl. No.: 10,544 I PrimaryExaminei.Henry .T. Klinksiek 52 us. 01 137/544, 302/23, 243/23,Ammo-Louis Bovasso and McCarthy 285/156 51 Int. 01 Fl6l41/00 1 TRACT v[58] Field of Search ..285/ 156; 15/104.06; 137/268, A method andapparatus for passing a pipeline sphere through 137/544 243/23 392/23 aflow tee disposed in a pipeline whereby fluid flowing through thepipeline may selectively be-flowed through at least one of [56]References Cited the outlets of the run of the flow tee or the branchoutlet of the UNITED STATES PATENTS v flow tee while preventing thesphere from entering branch 9 outlet. A gap is formed 1n the run of theflow tee at us uncuon 2,845,631 8/1958 KOZlOWSkl et al. ..285/ 178 Xwith th bran h outlet 3 that fluid may pass through either DaVlS X therun or the branch outlet when the mn.is occu ied 3 3,091,433 5/1963 y--285/156 X pipeline sphere. This gap is approximately equal to between3,387,483 6/1968 Van Arsdale 15/ 104.06 X 11,5 and 2 times the diameteifthe sphere 2,457,041 12/1948 Harza ..285/156 X 2,589,170 3/1952 2Clains, 5 Drawing Figures Ver Nooy 15/ 104.06

PATENTEDJULIB m2 3.671.292

FIG. 2

FIG. 5

PIPELINE FLOW TEE 1. Field of the Invention The invention relates topipeline flow tees; and, more particularly, to apparatus and method forpassing a pipeline sphere through the flow tee of a pipeline wherebyfluid flowing in the pipeline may be selectively flowed through at leastone of the run or the branch outlet of the flow tee.

2. Description of the Prior Art The accumulation of waxes, asphaltines,and scale in flow lines tends to restrict flow through such lines.Various chemical, mechanical and heating methods have been proposed forremoving deposits from the internal surfaces of flow lines, tubing,pipes and the like. Such mechanical methods include the use of apipeline cleaning plug or pig which is inserted into a pipeline andforced through the line by the pressure of the fluid flowingtherethrough to thereby remove deposits from the wall of the pipelineand thus (1) clean the pipeline of the aforementioned restrictions, (2)separate fluids, (3) apply coatings, and (4) measure the rate of flow.

A pipeline flow tee is a tee which allows fluid flow to go fromthe runof the tee out through the branch outlet thereof while a pipeline pig,such as a sphere, plug, or scraper, passes on through the run of thetee. The prime considerations for an adequate flow tee are (l) scraper,plug, and/or sphere handling characteristics, and (2) pressure dropscharacteristics. In regard to sphere, play and/or scraper handlingcharacteristics, the sphere, plug, or scraper should pass the flow tee,with the branch outlet thereof blocked, at all velocities which will beencountered, and should pass out the run of the tee and cause minimumsurge and pressure drop with the down-stream run of the tee blocked andall flow going through the branch outlet. Errors or malfunctions inbypass valve sequencing should not cause damage to the pipeline, sphere,plug, or scraper. In regard to pressure drop characteristics, the flowtee should cause a minimum of permanent pressure drop as a pressure dropsavings are directly related to power savings. Known prior art pipe teeshave the inherent characteristics of either excess friction loss at highvelocities or sphere-stalling at low velocities.

SUMMARY OF THE INVENTION It is an object of this invention to provide animproved method and apparatus for fluid flow through a pipeline flowtee.

It is a further object of this invention to provide a method andapparatus for fluid flow through a pipe tee wherein, at all velocitiesencountered in the tee, a pipeline sphere will pass through the run ofthe tee with the branch outlet blocked.

These and other objects are preferably accomplished by providing a flowtee which may be disposed in a pipeline whereby fluid flowing throughthe pipeline may be selectively flowed through the run of the flow teeor the branch outlet of the flow tee while preventing. the sphere fromentering the branch outlet. Gap means is formed in the run of the flowtee at its junction with the branch outlet so that fluid may passthrough either the run or out the branch when the run is occupied by thespheres. The gap provides adequate flow area with a sphere in the tee,and allows space for the sphere to decelerate with minimum pressuresurge if the run outlet is blocked. The gap also releases the sphere,leaving it free to move with the flow. Preferably, an inclined rampleads from the inlet of the run to the outlet thereof allowing a sphereto roll down the ramp and out of the flow tee at minimum flow rates.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top plan view of a pipe teein accordance with the teaching of our invention;

FIG. 2 is a vertical cross-sectional view of the pipe tee of FIG. 1;

FIG. 3 is a cross-sectional view of the pipe tee of FIGS. 1 and 2 takenalong line 3-3 of FIG. 2; and

FIGS. 4 and 5 are vertical sectional views of the pipe tee of FIGS. 1through 3 in operative position with a pipeline system showing alternatetypes of pipeline pigs circulating therethrough.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 of thedrawing, a pipe tee 10 is shown having a branch outlet 11 and a run 12.The branch outlet 11 terminates for coupling the branch outlet 11 to apipeline (not shown). The run 12 of pipe tee 10 includes an inlet 15 andan outlet 16. Inlet 15 and outlet 16 each terminate, respectively, forcoupling the run 12 of pipe tee 10 to a pipeline (not shown).

A gap 19 is formed at the junction of branch outlet 11 with run 12. Gap19 is substantially equal in length to the distance between front andrear scraper cups on a conventional pipeline pig (not shown)as will bediscussed further hereinbelow. An inclined ramp 20 (FIG. 2) extends fromthe inlet 15 v of the run 12 to the outlet 16 thereof. Thus, thelongitudinal axis of the inlet 15 to run 12 is offset to and slightlyabove the longitudinal axis of the outlet 16 of run 12. Bothlongitudinal axis, however, are parallel to each other as can be seen inFIG.

A longitudinal guide bar 21 extends across substantially the middle ofthe inlet 22 of the branch outlet 11 to run 12. In this manner, pipelinespheres or pigs are restrained from entering the branch outlet 11. A keypoint regarding the location of the restraining bar 21 and the gap 19 isthat they are combined in a manner to prevent the sphere (or pig) fromblocking the branch outlet, as seen in FIG. 3. By providing sufficientflow area around the sphere, the flow can pass around the sphere and outthe branch with minimum hydrodynamic force on the sphere when the runoutlet 16 is blocked downstream. This technique allows the bar 21 to beof lighter construction and reduces pressure drop.

Various arrangement may be used for forming pipe tee 10. For example, inthe embodiment illustrated in FIGS. 1 through 3, the pipe tee 10 may beformed by providing an oversized outer tee which comprises the branchoutlet 11 and a portion of the run 12 perpendicular to branch outlet 1l. The complete run 12 may be formed by telescopingly inserting inletand outlet portions 15 and 16 into the free ends of the oversizedportion of the'run 12 connected to branch outlet 11. The junctures ofthe component parts of the so-formed pipe tee 10 may be welded so that afluid-tight seal is provided. The inlet portion 15 of run 12 ispreferably provided with a tab 22a which forms ramp 20;-outlet portion16 is provided with a tab 23 which, together with tab 22a, forms gap 19.In this manner, a suitable gap area may be provided between portions 15and 16 and the run of the oversized outer tee.

Referring now to FIG. 4, the pipe tee 10 of FIGS. 1 through 3 is shownconnected to a pipeline 24. The arrow indicates the direction of flowthrough pipeline 24. This arrow corresponds to the arrow in FIG. 1 whichshows the direction of flow through pipe tee 10 when coupled to pipeline24. A conventional pipeline pig, in the form of a ball or sphere 25, isshown within the run 12 of pipe tee 10 and disposed in gap 19.Similarly, the pipeline pig in FIG. 5, in the form of a scraper 26having front end rear scraper cups, is shown disposed within gap 19. Gap19 in FIG. 5 is substantially equal in length to the distance betweenthe front and rear scraper cups, as for example, 5 /5 inches.

In both cases, with fluid flow through pipeline 24 in the direction ofthe arrow, the pipeline pig (either sphere 25 or scraper 26) enters therun 12 of pipeline tee 10. Bar 21 restrains the pig from entering branchoutlet 11. The pigs pass down ramp 20, and with the outlet 11 blocked,there is no pressure surge with the sphere 25, and only a minor surge(less than 10 psi) with the scraper 26 since, as can be seen in FIG. 4,fluid flows around the sphere through the remaining area of gap 19 outthe branch 11 with very little pressure loss. The length of the gap 19is made equal to the scraper 26 cup spacing. Thus, the rear cup pushesthe front cup through the gap,

and when the rear cup enters the gap, the front cup starts into outlet16. If outlet 16 is blocked, the front cup folds back and allows fluidto pass back. around the front cup as it is forced into the outlet 16.This causes a small rise in pressure (less than psi), since the rear cupquickly clears inlet and fluid can then bypass around the rear cup,through gap 19, and

pass out the branch 11. Note that the sloping ramp serves no purposewhenhandling scrapers. It allows spheres to roll down the ramp (andacross gap 19) at almost nil flow velocity. At velocities above 1 to 2feet per second, spheres move through the gap on'a flat track, e.g., thesloping ramp is not always necessary and might be deleted on someapplications.

Utilizing the pipeline flow tee 10 of our invention, errors ormalfunctions in bypass valve sequencing. will not cause damage to thepipeline, sphere or scraper. In regard to pressure drop characteristics,the use of flow tee 10 causes a minimum of permanent pressure drop.

Although only a single longitudinal guide bar 21 has been disclosed assufiicient to restrain a sphere from entering the branch, obviously aplurality of such bars may be provided for restraining pipeline pigsfrom entering outlet 11. However, while any number of longitudinal barswill not increase the risk of damage to pipeline pigs during passagethrough tee 10, multiple bars are objectionable from the standpoint ofpossibly trappinglarge objects, such as scraper parts, uninflatedspheres, skids, etc.. In both cases, however, only the bottom ramp (ortrack) 20 contacts the sphere or scraper within gap 19.

Pipeline pigs passing through the flow tee 10 as discussed hereinaboveare not circumferentially contacted by the walls of thetee or otherconstraining elements while located within the tee (where fluid flowthrough the run of the tee bypasses the pig). No orifices or outlets arerequired on the downstream run outlet. Because the pig is not grippedcircumferentially or held in the run, it moves in response to extremelylow hydrodynamic forces. The downwardly sloped ramp 20 allows the sphereto roll towards the downstream run outlet.

EXAMPLE The following is an illustrative example of the evaluation ofthe flow tee l0 installed in a pipeline. The fluid used was Texaco AlmagIndustrial Oil. A constant fluid temperature of 90 F. was used. At thistemperature, the Texaco Almag Oil has a specific gravity of 0.837 and akinematic viscosity of 7.6 centistokes. Pressure drop data was takenwith a U-tube mercury manometer indicating the differential pressure.Velocity measurements were taken by automatically timing the pipelinepig passage between two pipeline pig detectors located 51.83 feet apart.The pipeline pig was run through the flow tee at varying velocities withthe branch outlet blocked. The run of the flow tee was 4 inches indiameter, the branch outlet was 3 inches in diameter, and schedule 40size pipe was used throughout. The pressure drop was determined from thepressure upstream of the tee and on the branch 10 feet downstream fromthe branch outlet. in a separate data run, pressures were also takenbetween a point immediately downstream of the branch outlet on thebranch and the same point on the branch ten feet downstream from thebranch outlet. This procedure produced a correction which was applied tothe pipeline flow tee and this, along with a velocity head correction,gave the true total head loss across the pipeline flow tee. Theresistance coefiicient (K) and the equivalent length (L/ D) have beencalculated as a means of presenting a length. ratio (L/D) are based onthe tee run size. The L/D ratio was computed using the Fanning pressuredrop formula with friction factor for new (clean) steel pipe.

The following data was obtained showing the low pressure drops obtainedutilizing the flow tee of our invention:

Pressure Resistance Equiva- Velocity Flow Flow Drop Coeffilent (FPS)(GPM) (BPD) (PST) cient-K Length- L/D 1.5 61. 2104. 0.02 1.56 44. 4.0 I158. 5424. 0.10 1.13 41. 5.9 232. 7968. 0.22 1.13 45. 7.8 310. 10636.0.34 0.98 42. 9.2 364. 12480. 0.45 0.95 43. 10.0. 397. 13604. 0.53 0.9543.

We claim as our invention:

1. A pipeline flow tee adapted to pass a pipeline pig therethroughcomprising:

a run adapted to pass fluid having a substantially horizontal inletportion and a substantially horizontal outlet portion of the samediameter;

a branch outlet adapted to pass fluid connected to said run andsubstantially perpendicular thereto having an inlet portioncommunicating with the interior of said run and an outlet portioncommunicating with said branch outlet inlet portion, said branch outletand said run comprising a tee-shaped pipe section with a leg of saidtee-shaped pipe section forming said branch outlet and a pair oflongitudinally-extending pipe sections telescopingly fitting in each endof the run of said tee-shaped pipe section comprising the run of saidpipeline flow tee;

gap means formed in said run at the junction of said run with saidbranch outlet and adapted to pass fluid through said run when thejunction of said run with said branch outlet is occupied by a pipelinepig;

pipeline pig guiding means comprising a straight guide bar extendingacross substantially the middle of the inlet portion of said branchoutlet for restraining said pipeline pig passing through said run fromentering said branch outlet,

' said guide bar being spaced away from the inlet portion of said branchoutlet in such a manner that when a sphere is in said gap means, fluidmay flow around said sphere and out said branch outlet; and

an inclined ramp leading from the inlet portion of said run to theoutlet portion thereof, said ramp being adapted to roll said pipelinepig downwardly through said run when said run is oriented ina-horizontal direction with the longitudinal axis of the inlet portionof said run being uppermost with respect to the longitudinal axis of theoutlet portion of said run.

2. The flow tee of claim 1 wherein the pig is a sphere and the gap meanshas a diameter greaterthan the diameter of the sphere and a lengthapproximately equal to between l-% and 2 times the diameter of thesphere.

1. A pipeline flow tee adapted to pass a pipeline pig therethroughcomprising: a run adapted to pass fluid having a substantiallyhorizontal inlet portion and a substantially horizontal outlet portionof the same diameter; a branch outlet adapted to pass fluid connected tosaid run and substantially perpendicular thereto having an inlet portioncommunicating with the interior of said run and an outlet portioncommunicating with said branch outlet inlet portion, said branch outletand said run comprising a tee-shaped pipe section wIth a leg of saidtee-shaped pipe section forming said branch outlet and a pair oflongitudinally-extending pipe sections telescopingly fitting in each endof the run of said tee-shaped pipe section comprising the run of saidpipeline flow tee; gap means formed in said run at the junction of saidrun with said branch outlet and adapted to pass fluid through said runwhen the junction of said run with said branch outlet is occupied by apipeline pig; pipeline pig guiding means comprising a straight guide barextending across substantially the middle of the inlet portion of saidbranch outlet for restraining said pipeline pig passing through said runfrom entering said branch outlet, said guide bar being spaced away fromthe inlet portion of said branch outlet in such a manner that when asphere is in said gap means, fluid may flow around said sphere and outsaid branch outlet; and an inclined ramp leading from the inlet portionof said run to the outlet portion thereof, said ramp being adapted toroll said pipeline pig downwardly through said run when said run isoriented in a horizontal direction with the longitudinal axis of theinlet portion of said run being uppermost with respect to thelongitudinal axis of the outlet portion of said run.
 2. The flow tee ofclaim 1 wherein the pig is a sphere and the gap means has a diametergreater than the diameter of the sphere and a length approximately equalto between 1- 1/2 and 2 times the diameter of the sphere.